The desire to decrease and ultimately eliminate dependence on fossil fuels has stimulated research into clean and renewable ways to produce electricity for the global marketplace. Solar power has become a viable option because it is a clean form of energy production and there is a potentially limitless supply of solar radiation. To that end, it is estimated the solar energy flux from the sun is approximately 2.7 megawatt-hours per square meter per year in certain advantageous areas of the world. With this tremendous amount of free and clean energy available, together with the desire to reduce dependence on fossil fuels, solar power production has become a well recognized means for meeting a portion the energy needs in various countries around the world.
Technological innovations and improvements have moved terrestrial solar power generation into the range of feasible large scale power production. More specifically, the reduction in the magnitude of capital investment required and the reduction in recurring operation and maintenance costs allow solar power generation to compete with other forms of terrestrial power generation. Further, the scalability of solar power plants has the potential to provide smaller facilities, on the order of ten kilowatts, to communities with smaller demands and larger facilities, on order of one hundred megawatts, to large metropolitan areas with higher demand.
To address the above demand for solar power systems, many configurations have been designed and implemented. One such implementation is a concentrated solar power system that collects solar energy and concentrates that energy onto an absorber. The absorbed optical energy provides a source of thermal energy to operate a power conversion cycle, for example a heat engine. The heat engine then produces electricity that is eventually fed into the electrical grid.
A typical concentrated solar power system uses parabolic dishes for concentrators and Stirling engines for power conversion. Parabolic dish concentrators, however, are expensive. Further, the dish concentrator configuration has stringent two-axis pointing requirements to maintain the focus of the dish concentrator at the absorber and achieve the desired concentration of solar energy. Along with high capital costs for dish concentrators, the high temperatures at the focus of a dish concentrator can increase material and maintenance costs of the absorber and peripheral equipment. To adequately measure the above costs, a common metric, dollars per kilowatt-hour, is used to assess overall solar power system efficiency. Any reduction, therefore, in capital expenditures or recurring maintenance and operational expenses, while being able to produce comparable power output, will result in an overall cost savings in the operation of such a solar power system.
Replacement of the dish concentrator with a trough concentrator has the potential to significantly decrease the capital costs of a solar power generation system and eliminates the need for stringent two-axis pointing system. The high temperature point focus is now replaced with a moderate temperature line focus. A linear absorber is used on the line focus of the trough concentrator utilizing a vacuum jacketed tube to provide efficient collection of the solar energy. Nevertheless, the above changes must not adversely affect the basic efficiency of the solar power system configuration.